Power conversion device

ABSTRACT

Provided is a power converter  3  that directly converts polyphase AC power to AC power. A converter circuit has a plurality of first switching elements  311, 313  and  315  and a plurality of second switching elements  312, 314  and  316 , both of which are connected to each phase R, S or T of the polyphase AC power to enable switching for turning on current-carrying bidirectionally. Condensers  821  to  826  are provided between phases. Input terminals of the first switching elements and those of the second switching elements are arranged to form respective lines. Some of the plurality of condensers  821  and  822  are arranged to be angled relative to the arrangement direction of the terminals. The wiring distance between the condensers and the switching elements can be shortened.

TECHNICAL FIELD

The present invention relates to a power conversion device or a powerconverter that directly converts AC power of commercial frequency to anarbitrary PC power.

BACKGROUND ART

As a power converter that has the small number of components to enabledownsizing of the device and directly and effectively converts AC powerto AC power, a matrix-converter has been known (Patent Document 1).

In the above-mentioned conventional matrix-converter, filter condensersconstituting a filter circuit are arranged on a substrate forming a linein a longitudinal direction and installed in a unit case. However, insuch arrangement, the wiring for connecting IGBTs (viz., Insulated GateBipolar Transistor), which are switching means, to the filter condensershas a long length undesirably.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese Laid-open Patent Application (Tokkai)2006-333590

SUMMARY OF INVENTION

An object of the present invention is to provide a power converter thatcan shorten the wiring distance between the filter condensers and theswitching means.

In the present invention, some of the filter condensers are angledrelative to a direction in which terminals of switching elements arearranged.

According to the present invention, the distance between some of thefilter condensers and the switching elements and the distance betweenthe other filter condensers and the switching elements can besubstantially equalized, and thus, the wiring distance between thefilter condensers and the switching elements can be shortened.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an electrical diagram showing a power conversion system towhich an embodiment of the present invention is practically applied.

FIG. 2A is a plan view of a power converter of the embodiment of thepresent invention in an assembling process.

FIG. 2B is another plan view of the power converter of the embodiment ofthe present invention in the assembling process.

FIG. 2C is still another plan view of the power converter of theembodiment of the present invention in the assembling is process.

FIG. 2D is a side view of the power converter of the embodiment of thepresent invention in the assembling process.

FIG. 3 shows plan and side views depicting a layout of IGBTs and filtercondensers of the power converter of FIG. 2.

FIG. 4A is a plan view depicting another layout of IGBTs and filtercondensers shown in FIG. 3.

FIG. 4B is a side view of FIG. 4A.

FIG. 5 shows plan and side views depicting still another layout of IGBTsand filter condensers shown in FIG. 3.

FIG. 6 shows plan and side views depicting another layout of IGBTs andfilter condensers shown in FIG. 3.

FIG. 7 is an electrical diagram showing a power conversion system towhich another embodiment of the present invention is practicallyapplied.

FIG. 8 shows plan and side views depicting a layout of IGBTs and filtercondensers of the power converter of FIG. 7.

FIG. 9 shows plan and side views depicting another layout of IGBTs andfilter condensers of the power converter of FIG. 7.

EMBODIMENTS FOR CARRYING OUT INVENTION

[Outline of Power Conversion System 1]

First, a brief outline of a power conversion system to which anembodiment of the present invention is practically applied will bedescribed with reference to FIG. 1. The power conversion system 1 ofthis example is a system in which a three-phase AC power supplied from athree-phase AC power supply 2 is directly converted to a single-phase ACpower by a power converter 3 of the embodiment of the present invention,and after the voltage of the converted AC power is stepped up or down bya transformer 4 to a suitable value, the transformed AC power isconverted by a rectifier 5 to a DC power to charge a secondary battery6. It is to be noted that denoted by numeral 7 is a smoothing circuit.

In power conversion system 1 of this example, output lines (indicated byR-phase, S-phase and T-phase) to which the three-phase AC power issupplied from three-phase AC power supply 2 have at each phase a filtercircuit 8 that dampens a higher harmonic wave for suppressing noise.Filter circuit 8 of this example comprises three filter reactors 81respectively connected to the R, S and T phases and six filtercondensers 82L and 82R each being connected between the R, S and Tphases. The layout of filter condensers 82L and 82R (which are indicatedas filter condensers 821 to 836 in FIGS. 3 to 6) will be describedhereinafter.

In power conversion system 1 of this example, the three-phase AC poweris supplied to power converter 3 through filter circuit 8 and convertedinto the single-phase AC power. Power converter 3 of this example isequipped with six bidirectional switching elements 31 that are arrangedin a matrix shape corresponding to the R, S and T-phases. In thefollowing, when one bidirectional switching element is to be genericallydescribed, explanation will be made with the aid of reference numeral31, while, as is shown in FIG. 1, when a specified one of the sixbidirectional switching elements is to be described, explanation will bemade by using reference numerals 311 to 316.

Each of bidirectional switching elements 31 of this example isconstructed of an IGBT module in which IGBT (viz., Insulated GateBipolar Transistor), which is a semi-conductor switching element, andreflux diodes are combined and connected through an inverse-parallelconnection. It is to be noted that each of bidirectional switchingelements 31 is not limited to the illustrated one. That is, theswitching element may have the other construction. For example, theswitching element may have a construction in which two elements ofreverse-blocking type IGBT are connected through an inverse-parallelconnection.

Each of bidirectional switching elements 31 is equipped with a snubbercircuit 32 for protecting bidirectional switching element 31 from asurge voltage inevitably produced when bidirectional switching element31 is subjected to ON/OFF operation, snubber circuit 32 including acombination of one snubber condenser and three diodes which are arrangedat input and output sides of bidirectional switching element 31. In thefollowing, when one snubber circuit is to be generally described,explanation will be made with the aid of reference numeral 32, while, asis shown in FIG. 1, when a specified one of the six snubber circuits isto be described, explanation will be made by using reference numerals321 to 326.

Power conversion system 1 of this example is equipped with amatrix-converter control circuit 9 for effecting ON/OFF control ofbidirectional switching elements 31 of power converter. In thematrix-converter control circuit 9, a value of voltage supplied from thethree-phase AC power supply 2, a value of DC current that is beingoutputted and a target level of order current are inputted, andthereafter, based on them, respective gate signals of the bidirectionalswitching elements 31 are controlled to adjust the single-phase AC powerdirected to the transformer 4. With this, a target direct-current poweris obtained.

Transformer 4 functions to step up or down the voltage of thesingle-phase AC power, which has been converted by power converter 3, toa desired value. Rectifier 5 is equipped with four rectifying diodes toconvert the adjusted single-phase AC power to a direct-current power.Smoothing circuit 7 is equipped with a coil and a condenser forsmoothing the pulsating current contained in the rectified directcurrent so that the pulsating current is smoothed to show a shape muchsimilar to a direct current.

By power conversion system 1 having the above-mentioned construction,the three-phase AC power from three-phase AC power supply 2 is directlyconverted by power converter 3 to the single-phase AC power, and afterthe converted single-phase AC power is adjusted in voltage, the adjustedsingle-phase AC power is converted to the direct-current power. Withthis, secondary battery 6 is charged. It is to be noted that theabove-mentioned power conversion system 1 is one of exemplified systemsto which power converter 3 of the present invention is practicallyapplied and the present invention is not limited to application to onlythe above-mentioned power conversion system 1. That is, when at leastone of an electric power that is to be converted and an electric powerthat has been converted is a polyphase AC power, the present inventionis applicable to other power conversion systems.

[Part Arrangement of Power Converter 3]

Then, spatial arrangement of parts that constitute power converter 3 ofFIG. 1 will be described with reference to FIGS. 2 to 6. It is to benoted that parts identical to those shown in FIG. 1 are indicated by thesame reference numerals for showing mutual relation between them.

FIG. 2 includes FIGS. 2A to 2D. FIG. 2A is a plan view in an assemblingprocess showing six bidirectional switching elements 31 (each beingcalled as IGBT module) mounted on an upper surface of a heat sink 10.FIG. 2B is a plan view in the assembling process showing, in addition tothe bidirectional switching elements, bus bars that are provided toconnect terminals of bidirectional switching elements 31. FIG. 2C is aplan view in the assembling process of three diodes that are parts ofsnubber circuit 32 and filter condensers 82 of filter circuit 8, showingthe left side three filter condensers mounted. FIG. 2D is a side view ofthe above-mentioned device. Since parts that constitute power converter3 of the present invention are mutually overlapped when viewed in aplane, the following explanation on essential portions will be made withthe aid of the other drawings.

As is shown in FIGS. 2 and 3, each bidirectional switching element 31 ofthis example is provided at an upper surface of a module package withinput and output terminals and an intermediate terminal that is one oftwo intermediate terminals respectively provided by paired two IGBTs.Among the six bidirectional switching elements 311 to 316 shown in FIG.3, the left side three bidirectional switching elements 311, 313 and 315have each the input terminal at the left end, the output terminal at theright end and the intermediate terminal at the middle. Furthermore,among the six bidirectional switching elements 311 to 316 shown in FIG.3, the right side three bidirectional switching elements 312, 314 and316 have each the input terminal at the right end, the output terminalat the left end and the intermediate terminal at the middle. Although agate terminal of each bidirectional switching element 31 is mounted to aportion other than the module package, illustration of the gate terminalis omitted.

As is seen from FIGS. 2 and 3, the six bidirectional switching elements311 to 316 are fixed to the upper surface of heat sink 10 throughconnecting means such as bolts or the like. As is seen from suchdrawings, the six bidirectional switching elements 311 to 316 are soarranged that paired bidirectional switching elements 311 and 312,paired bidirectional switching elements 313 and 314 and pairedbidirectional switching elements 315 and 316 are placed on the left andright sides respectively with respect to a center line CL. In otherwords, the two bidirectional switching elements 311 and 312, twobidirectional switching elements 313 and 314 and two bidirectionalswitching elements 315 and 316, which are each paired with respect to adirection in which the three terminals (viz., input terminal,intermediate terminal and output terminal) of each bidirectionalswitching element 31 extend, are respectively placed on the left andright sides with respect to the center line CL. In the following, thisarrangement will be reworded as “being arranged abreast with respect tothe center line CL or output lines P and N each connecting the outputterminals”. It is to be noted that the arrangement is different fromthat shown in FIG. 5 which will be described hereinafter. It is furtherto be noted that paired bidirectional switching elements mean a pair ofbidirectional switching elements that are connected to the same phase R,S or T of input line.

By arranging paired bidirectional switching elements 311 and 312, pairedbidirectional switching elements 313 and 314 and paired bidirectionalswitching elements 315 and 316 on the left and right sides respectivelywith respect to the center line CL as is described hereinabove, it ispossible to provide a layout in which output lines P and N (bus bars 331and 332) are drawn in one direction with the shortest distance. If thelength of wiring arrangement through which a high frequency AC power isoutputted is long, the arrangement is easily influenced by L-component.However, in the wiring arrangement according to the invention, influenceby L-component can be suppressed. This suppression is an advantageouseffect as compared with the arrange of the other example of FIG. 5. Thatis, output lines P and N show nearly straight lines until reachingtransformer 4.

Furthermore, as is mentioned hereinabove, the terminals provided atright ends of bidirectional switching elements 311, 313 and 315 placedat the left side with respect to the center line CL are all outputterminals, and the terminals provided at left ends of them are all inputterminals. While, the terminals provided at left ends of bidirectionalswitching elements 312, 314 and 316 placed at the right side withrespect to the center line CL are all output terminals, and theterminals provided at right ends of them are all input terminals.

To the input terminals provided at the left ends of bidirectionalswitching elements 311, 313 and 315 placed at the left side with respectto the center line CL, there are connected input lines R, S and T of onegroup branched from input lines from three-phase AC power supply 2, theinput lines R, S and T of one group extending toward the center line CL,and to the input terminals provided at the right ends of bidirectionalswitching elements 312, 314 and 416 placed at the right side withrespect to the center line CL, there are connected input lines R, S andT of the other group branched from the input lines from three-phase ACpower supply 2, the input lines R, S and T of the other group extendingtoward the center line CL. That is, to the input terminals ofbidirectional switching elements 311 and 312, there is connectedR-phase, to the input terminals of bidirectional switching elements 313and 314, there is connected S-phase and to the input terminals ofbidirectional switching elements 315 and 316, there is connectedT-shape. By making a direction in which the left and right input linesR, S and T extend for the connection with the input terminals equal tothe direction toward the center line CL, a distance of heat sink 10 inthe left-and-right direction can be reduced as compared with that ofanother arrangement shown in FIG. 6.

In the arrangement of FIG. 1, input lines R, S and T from three-phase ACpower supply 2 to power converter 3 are branched at a position between aunit of filter reactors 81 and a unit of filter condensers 82L and 82R.However, a modification may be employed in which the branching is madeat an upstream position of filter reactors 81 and the input lines R, Sand T thus branched are respectively provided with filter reactors 81.

To the output terminals provided at the right ends of bidirectionalswitching elements 311, 313 and 315 placed at the left side with respectto the center line CL, there is connected one bus bar 331 thatconstitutes output line P of power converter 3, and to the outputterminals provided at the left ends of bidirectional switching elements312, 314 and 316 placed at the right side with respect to the centerline CL, there is connected one bus bar 332 that constitutes output lineN of power converter 3. Leading ends of these bus bars 331 and 332 areconnected to transformer 4. These bus bars 331 and 332 andafter-mentioned bus bars are constructed of an electrically conductivebody having good conductivity, such as copper or the like.

The input terminals of paired bidirectional switching elements 311 and312 placed at the left and right sides with respect to the center lineCL are connected through a bus bar 333, the input terminals ofbidirectional switching elements 313 and 314 are connected through a busbar 334 and the input terminals of bidirectional switching elements 315and 316 are connected through a bus bar 335. In an equivalent circuit ofFIG. 1, wirings corresponding to such bus bars are indicated by the samereference numerals. In view of the function of power converter 3, thesebus bars 333 to 335 are not essential. Thus, these bus bars may beomitted.

When viewed in a plan view, these bus bars 333 to 335 are arranged tocross bus bars 331 and 332 that constitute output lines P and N.However, as is seen from the side view of FIG. 3, bus bars 333 to 335that connect the opposed input terminals are arranged at a positionhigher than bus bars 331 and 332 of output lines P and N, and thus aso-called overhead crossing is provided between them thereby to cause nomutual interference therebetween.

By connecting paired bidirectional switch elements 311 and 312 placed atthe left and right sides with respect to the center line CL, pairedbidirectional switching elements 313 and 314 and paired bidirectionalswitching elements 315 and 316, filter condensers 82L and 82R each beinginterposed between the phases can be shared with each other. That is,between R-phase and S-phase shown in the left side of FIG. 1, there isarranged a filter condenser 821, and between R-phase and S-phase shownin the right side of the drawing, there is arranged a filter condenser824, and the input terminals of bidirectional switching elements 311 and312 to which R-phase is inputted are connected through bus bar 333.Accordingly, noise on R-phase of three-phase AC power supply 2 isfiltered by the two filter condensers 821 and 824 that cooperate witheach other, and thus, each filter condenser can be made small incapacity resulting in that each filter condenser can be made small insize. Also in S-phase and T-phase, similar advantage is obtained fromthe cooperation of two filter condensers.

In this example, filter circuit 8 has six filter condensers 821 to 826,and as is seen from FIG. 3, the input lines placed at the left and rightsides with respect to the center line CL are provided with three filtercondensers respectively. The left side filter condenser 821 is disposedbetween R-phase corresponding to input terminal of bidirectionalswitching element 311 and S-phase. Like this, the left side filtercondenser 822 is disposed between S-phase corresponding to the inputterminal of bidirectional switching element 313 and T-phase, and theleft side filter condenser 823 is disposed between T-phase correspondingto the input terminal of bidirectional switching element 315 andR-phase. While, the right side filter condenser 824 is disposed betweenR-phase corresponding to the input terminal of bidirectional switchingelement 312 and S-phase, the right side filter condenser 825 is disposedbetween S-phase corresponding to the input terminal of bidirectionalswitching element 314 and T-phase, and the right side filter condenser826 is disposed between T-phase corresponding to the input terminal ofbidirectional switching element 316 and R-phase.

As is mentioned hereinabove, by arranging, to the six bidirectionalswitching elements 311 to 316 which are arranged in such a manner thatthree elements and the other three elements are respectively placed atthe left and right sides with respect to the center line CL, the sixfilter condensers 821 to 826 in such a manner that three condensers andthe other three condensers are respectively placed at the left and rightsides with respect to the center line CL, the wiring distance ofconnecting wiring between each of filter condensers 821 to 826 andcorresponding one of bidirectional switching elements 311 to 316 can beshortened.

In this example, the six filter condensers 821 to 826 of which threefilter condensers and the other three filter condensers are arranged atthe left and right sides respectively are arranged outside an area wherethe six bidirectional switching elements 311 to 316 are placed withrespect to the center line CL. Specifically, as is shown by FIG. 2D, thefilter condensers are fixed to upper portions of the bus bars. Byarranging filter condensers 821 to 826 outside the area of bidirectionalswitching elements 311 to 316, the distance in the left-right directionbetween the left side bidirectional switching elements 31L and the rightside bidirectional switching elements 31R can be made shortest, andthus, a distance in the left-right direction of heat sink 10 can be setto the shortest resulting in that heat sink 10 can be made small in sizeas compared with a heat sink shown in FIG. 4A that shows the otherexample.

In the following, a mounting state of the filter condensers 821 to 826which are divided into two groups (each including three filtercondensers) placed on the left and right sides respectively with respectto the center line CL will be described with reference to the plan andside views of the real device of FIG. 2.

Before its description, a connecting structure of the bus bars will bedescribed. As is seen from FIG. 2B, bus bar 331 is the output line Pthat connects the output terminals of bidirectional switching elements311, 313 and 315 and leads to transformer 4, and bus bar 332 is theoutput line N that connects the output terminals of bidirectionalswitching elements 312, 314 and 316 and leads to transformer 4. Bus bar333 is a bus bar for connecting the input terminals of bidirectionalswitching elements 311 and 312, and bus bar 333 has extension portionsextending outward in the left and right directions from the respectiveinput terminals and the extension portions are respectively connected tobus bars 336 and 337 for connecting to filter condensers 823 and 826(the state of connection of these bus bars to filter condensers 823 and826 is understood from FIGS. 2C and 3). Bus bars 336 and 337respectively connected to opposed ends of bus bar 333 are angledrelative to a line that connects the input terminals of bidirectionalswitching elements 311, 313 and 315, that is a line that extends in theupward-and-downward direction in FIG. 2C.

Bus bar 334 is a bus bar for connecting the input terminals ofbidirectional switching elements 313 and 314, and bus bar 334 hasextension portions extending outward in the left and right directionsfrom the respective input terminals and the extension portions arerespectively connected to bus bars 338 and 339 for connecting to filtercondensers 821, 822, 824 and 825 (the state of connection of these busbars to filter condensers 821, 822, 824 and 825 is understood from FIGS.2C and 3). Bus bars 338 and 339 respectively connected to opposed endsof bus bar 334 extend along a line that connects the input terminals ofbidirectional switching elements 311, 313 and 315, that is a line thatextends in the upward-and-downward direction at the upper-left portionof FIG. 2.

Bus bar 335 is a bus bar for connecting the input terminals ofbidirectional switching elements 315 and 316, and bus bar 335 hasextension portions extending outward in the left and right directionsfrom the respective input terminals and the extension portions arerespectively connected to bus bars 340 and 341 for connecting to filtercondensers 823 and 826 (the state of connection of these bus bars tofilter condensers 823 and 826 is understood from FIGS. 2C and 3). Busbars 340 and 341 respectively connected to opposed ends of bus bar 335are angled relative to a line that connects the input terminals ofbidirectional switching elements 311, 313 and 315, that is a line thatextends in the upward-and-downward direction in FIG. 2C.

As is seen from FIG. 2D, these bus bars 333, 334 and 335 are connectedto the input terminals of bidirectional switching elements 311 to 316through several bus bars 345 and 346 and positioned higher than bus bars331 and 332 that constitute output lines P and N. With this, bus bars333 to 335 and bus bars 331 and 332 are arranged to constitute anoverhead crossing therefor leaving a predetermined space therebetween,causing no mutual interference therebetween.

As is shown by broken lines in FIG. 2C, filter condensers 821, 822 and823 are positioned outside with respect to the center line CL andarranged in such a manner that centers of filter condensers 821, 822 and823 are respectively placed at apexes of a triangle (isosceles triangleor equilateral triangle is preferable) of which one apex is directedoutward. By arranging the three filter condensers 821, 822 and 823 atthe apexes of the triangle, the wiring length between the condensers canbe made shortest and thus, power converter 3 can be made small in sizeand synchronization between the condensers can be assured. Furthermore,due to the arrangement with one apex being directed outward, the balanceof wiring of the condensers is improved as compared with an arrangementin which the apex is directed inward, and distances to respective busbars 333, 334 and 335 can be shortened. Bus bars 336 and 340 or bus bars337 and 341, which are connected to filter condenser 823 or 826respectively, are angled to each other to shorten the distancetherebetween. With this arrangement, the distances from filter condenser823 or 826 to respective bus bars 333 and 335 can be much shortened, andthus, equalization of wiring lengths between the condensers is assured.Furthermore, due to the arrangement in which bus bars 338 and 339 arearranged to extend in a direction perpendicular to the longitudinaldirection of bus bar 334, filter condensers 821, 822, 824 and 825 can beactually mounted without considering the sizes thereof, and thus, thedegree of freedom in designing of the condensers can be increased.

Filter condenser 821 disposed between R-phase and S-phase is mounted onan upper surface of bus bar 342 and filter condenser 822 disposedbetween S-phase and T-phase is mounted on an upper surface of bus bar343. These two bus bars 342 and 343 are connected while being angledrelative to a line that connects the input terminals of bidirectionalswitching elements 311, 313 and 315, that is, a line that extends in theupward-and-downward direction in FIG. 2C. Furthermore, these two busbars 342 and 343 are connected to bus bars 333, 342 and 335 whilestraddling a line that connects the input terminals of bidirectionalswitching elements 311, 313 and 315, that is a line that extends in theupward-and-downward direction in FIG. 2C. It is to be noted that filtercondensers 824 and 825 mounted at the right side of the center line CLare symmetrically arranged relative to filter condensers 821 and 822with respect to the center line CL.

By arranging bus bars 342 and 343 in such a manner that these bus barsare angled relative to the line that connects the input terminals ofbidirectional switching elements 311, 313 and 315, synchronization amongfilter condensers 821, 822 and 823 is assured because the wiringdistance between the filter condensers can be finely equalized with thewiring distance of filter condenser 823 disposed between R-phase andT-phase. Furthermore, by arranging bus bars 342 and 343 in such a mannerthat these bus bars straggle the line that connects the input terminalsof bidirectional switching elements 311, 313 and 315, the connectingdistance between filter condensers 821 and 822 and bus bars 333, 334 and335 can be shortened, and thus, power converter 3 can be made small insize. Furthermore, by arranging filter condensers 821 to 826 on uppersurfaces of the bus bars, that is, by arranging filter condensers 821 to826 at an opposite side of bidirectional switching elements 311 to 316with respect to the bus bars, the degree of freedom in designing layoutof filter condensers 821 to 826 is increased.

Filter condenser 823 disposed between R-phase and T-phase is mounted onan upper surface of bus bar 344 disposed between bus bars 336 and 340,and bus bar 344 is arranged to extend in parallel with a line thatconnects the input terminals of bidirectional switching elements 311,313 and 315.

In the following, an exemplified mounting of three diodes and onesnubber condenser which constitute one snubber circuit 32 shown in FIG.1 will be described. As is shown in FIG. 1, snubber circuit 321, forexample, of bidirectional switching element 311 has one terminalconnected to the input terminal of bidirectional switching terminal 311,another terminal connected to the intermediate terminal of bidirectionalswitching element 311 and still another terminal connected to the outputterminal of bidirectional switching element 311. Accordingly, as will beunderstood from FIGS. 2C and 2D, the three diodes are fixed andconnected to brackets 351 to 356 which are each constructed of anelectrically conductive body connected to an intermediate terminalbetween each bidirectional switching element 31L and correspondingbidirectional switching element 31R. In FIG. 2D, only bracket 355 isshown.

In this example, a relatively large-sized electrolytic condenser is usedas the snubber condenser, and the relatively large-sized electrolyticcondenser is used as a common snubber condenser 327 (see FIG. 3) for thesix snubber circuits 321 to 326. For connecting snubber condenser 327and the three diodes, there are provided bus bars 347 and 348 that areplaced between bus bars 331 and 332 and extend in the same direction asthese bus bars 331 and 332, the bus bars 331 and 332 constituting theoutput lines P and N.

As is seen from FIGS. 2D and 3, the two bus bars 347 and 348 connectedto snubber condenser 327 are fixed to a position that is higher than busbars 331 and 332 that constitute the output lines P and N but lower thanbus bars 333, 334 and 335. It is to be noted that these two bus bars 347and 348 are supported on heat sink 10 or a base (not shown) other thanthe heat sink. For preventing a short-circuit with bus bars 333, 334 and335, outer surfaces of bus bars 347 and 348 may be coated with aninsulating material.

Arrangement of bus bars 347 and 348 with respect to bus bars 331 and 332that constitute output lines P and N and snubber condenser 327 is asfollows. That is, by arranging bus bars 347 and 348 between bus bars 331and 332, both the wiring distance to output lines P and N and the wiringdistance to snubber condenser 327 can be shortened. Furthermore, byarranging bus bars 347 and 348 higher than bus bars 331 and 332, it ispossible to shorten the distance from the diodes of each of snubbercircuits 321 to 326.

According to the above-mentioned embodiment, the following advantagesare obtained.

1) In this example, to the six bidirectional switching elements 311 to316 which are arranged in such a manner that three elements and theother three elements are respectively placed at the left and right sideswith respect to the center line CL, there are arranged the six filtercondensers 821 to 825 in such a manner that three condensers and theother three condensers are respectively placed at the left and rightsides with respect to the center line CL, so that the wiring distance ofconnecting wiring between each of filter condensers 821 to 823 andcorresponding one of bidirectional switching elements 311 to 316 can beshortened.

2) In this example, since paired bidirectional switching elements 311and 312, paired bidirectional switching elements 313 and 314 and pairedbidirectional switching elements 315 and 316 are each arranged at theleft and right sides respectively with respect to the center line CL, itis possible to provide a layout in which output lines P and N (viz., busbars 331 and 332) are drawn in one direction with the shortest distance.If the length of wiring arrangement through which a high frequency ACpower is outputted is long, the arrangement is easily influenced byL-component. However, in the wiring arrangement according to theinvention, influence by L-component can be suppressed.

3) In this example, the six filter condensers 821 to 826 of which threefilter condensers and the other three filter condensers are arranged atthe left and right sides respectively are arranged outside an area wherethe six bidirectional switching elements 311 to 316 are placed withrespect to the center line CL. Thus, the distance in the left-and-rightdirection between the left side bidirectional switching elements 31L andthe right side bidirectional switching elements 31R can be madeshortest. Accordingly, the distance in the left-and-right direction ofheat sink 10 can be set to the shortest resulting in that heat sink 10can be reduced in size.

4) In this example, the input terminals of paired bidirectionalswitching elements 311 and 312, the input terminals of pairedbidirectional switching elements 313 and 314 and the input terminals ofpaired bidirectional switching elements 315 and 316, which are arrangedat the left and right sides with respect to the center line CL, areconnected through respective bus bars 333, 334 and 335. Accordingly,filter condensers 82L and 82R each being disposed between the phases canbe shared. Thus, each filter condenser can be made small in capacityresulting in that each filter condenser can be made small in size.

5) In this example, since the direction in which the left and rightinput lines R, S and T extend for the connection with the bidirectionalswitching elements 31L and 31R, is made equal to the direction towardthe center line CL, a distance of heat sink 10 in the left-and-rightdirection can be made small.

6) In this example, filter condensers 821 to 826 are arranged on uppersurfaces of the bus bars, that is, filter condensers 821 to 826 arearranged at an opposite side of bidirectional switching elements 311 to316 with respect to the bus bars, the degree of freedom in designinglayout of filter condensers 821 to 826 is increased.

7) In this example, the arrangement of bus bars 347 and 348 relative tobus bars 331 and 332 that constitute output lines P and N and snubbercondenser 327 is so made that bus bars 347 and 348 are placed betweenbus bars 331 and 332, so that both the wiring distance to output lines Pand N and the wiring distance to snubber condenser 327 are shortened.

8) In this example, since bus bars 347 and 348 are arranged higher thanbus bars 331 and 332, it is possible to shorten the distance from thediodes of each of snubber circuits 321 to 326.

9) In this example, since the three filter condensers 821, 822 and 823are arranged at the apexes of the triangle, the wiring length betweenthe condensers can be made shortest and thus, power converter 3 can bemade small in size, and synchronization between the condensers can beassured.

10) In this example, since an apex of the triangle at which one of thethree filter condensers is arranged is directed outward, the balance ofwiring of the condensers is improved as compared with an arrangement inwhich the apex is directed inward and the distances to bus bars 333, 334and 335 can be shortened.

11) In this example, since bus bars 342 and 343 are arranged to beangled relative to the line that connects the input terminals ofbidirectional switching elements 311, 313 and 315, the wiring distancebetween the filter condensers can be finely equalized with the wiringdistance of filter condenser 823 disposed between R-phase and T-phase.Accordingly, synchronization among filter condensers 821, 822 and 823can be assured.

12) In this example, since bus bars 342 and 343 are arranged to stragglethe line that connects the input terminals of bidirectional switchingelements 311, 313 and 315, the connecting distance between filtercondensers 821 and 822 and bus bars 333, 334 and 335 can be shortened,and thus, power converter 3 can be made small in size.

[Other Embodiments]

The present invention has modifications and embodiments other than theabove-mentioned embodiment. In the following, modifications of theinvention will be described. The present invention is not limited to theabove-mentioned embodiment and the following embodiments. In thefollowing, parts identical to those described in the above-mentionedembodiment are indicated by the same reference numerals and explanationon the same parts will be suitably omitted.

In the above-mentioned embodiment, as is shown in FIG. 3, the three leftside filter condensers 82L and the three right side filter condensers82R are arranged outside an area of bidirectional switching elements311, 313 and 315 and an area of bidirectional switching elements 312,314 and 316 respectively with respect to the center line CL. However, asis seen from FIGS. 4A and 4B, the three left side filter condensers andthe three right side condensers may be arranged between an area of theleft side bidirectional switching elements 311, 313 and 315 and an areaof the right side bidirectional switching elements 312, 314 and 316 withrespect to the center line CL.

In the above-mentioned embodiment, as is shown in FIG. 3, the sixbidirectional switching elements 311 to 316 are so arranged thatbidirectional switching elements 311, 313 and 315 and bidirectionalswitching elements 312, 314 and 316 are arranged at the left and rightsides respectively with respect to the center line CL. However, as isshown in FIG. 5, bidirectional switching elements 311, 313 and 315 andbidirectional switching elements 312, 314 and 316 may be arranged alongthe center line CL.

In the above-mentioned embodiment, as is shown in FIG. 3, the sixbidirectional switching elements 311 to 316 are so arranged thatbidirectional switching elements 311, 313 and 315 and bidirectionalswitching elements 312, 314 and 316 are arranged at the left and rightsides respectively with respect to the center line CL and the input andoutput terminals of the left side bidirectional switching elements andthe input and output terminals of the right side bidirectional switchingelements are arranged in line symmetry with respect to the center lineCL. However, as is shown in FIG. 6, an arrangement may be employed inwhich bidirectional switching elements 311, 313 and 315 andbidirectional switching elements 312, 314 and 316 are arranged at theleft and right sides with respect to the center line CL and the inputand output terminals of the left side bidirectional switching elementsand the input and output terminals of the right side bidirectionalswitching elements are arranged in the same manner. In this case, inputlines R, S and T of the dual system are connected to the input terminalsof the left and right side bidirectional switching elements whileextending in the same direction (in the direction from left to right inthe illustrated example).

In the above-mentioned embodiment, as is shown in FIG. 3, filtercondensers 821 to 826 are arranged between the phases while keepingone-to-one relation to the six bidirectional switching elements 311 to316. However, as is shown in FIG. 7, an arrangement may be employed inwhich filter condensers 821 to 826 are arranged between the phases insuch a manner that several (two in the illustrated example) of thefilter condensers 821 to 826 are connected to each of the sixbidirectional switching elements 311 to 316.

In this case, the filter condensers may be arranged at the center ofpower converter 3 as is shown in FIG. 8 or outside power converter 3 asis shown in FIG. 9. As will be understood from FIG. 8, when the filtercondensers are arranged at the center of power converter 3, empty spacesare usable, so that the size of power converter 3 can be made as smallas possible.

The above-mentioned bidirectional switching elements 311, 313 and 315correspond to first switching elements in Claims, the above-mentionedbidirectional switching elements 312, 314 and 316 correspond to secondswitching elements in Claims, the above-mentioned power converter 3corresponds to a converter circuit in Claims, the above-mentioned filtercondensers 821 to 826 and 831 to 836 correspond to condensers in Claimsand the above-mentioned bus bars 331 and 332 correspond to output linesin Claims.

The invention claimed is:
 1. A power converter that directly convertspolyphase AC power to AC power, the power converter comprising: aconverter circuit including a plurality of first switching elements thatare connected to each phase of the polyphase AC power to enableswitching for turning on current-carrying bidirectionally and aplurality of second switching elements that are connected to each phaseto enable switching for turning on current-carrying bidirectionally; anda plurality of condensers connected to the converter circuit, wherein atleast one of the condensers is disposed between phases of the polyphaseAC power applied to the first switching elements and between phases ofthe polyphase AC power applied to the second switching elements; andwherein a spatial arrangement is provided by: an arrangement in whichterminals of the plurality of first switching elements are physicallyand geometrically arranged in a line and terminals of the plurality ofsecond switching elements are physically and geometrically arranged in aline; and an arrangement in which some of the plurality of condensersare physically and geometrically arranged to be angled relative to thelines that the terminals form.
 2. A power converter as claimed in claim1, in which connecting terminals provided at both ends of each of thesome condensers are arranged to put therebetween a line that connects aplurality of terminals arranged in a line.
 3. A power converter asclaimed in claim 1, in which the other condensers of the plurality ofcondensers are physically and geometrically arranged in parallel withthe arrangement direction of the terminals.
 4. A power converter asclaimed in claim 3, in which wirings for connecting the other condensersto the phases are arranged to be angled relative to the arrangementdirection of the terminals.
 5. A power converter as claimed in claim 1,further comprising: a first bus bar that extends in a directionperpendicular to the arrangement direction of the terminals, the firstbus bar being connected to at least one of the first and secondswitching elements that correspond to one of the phases; a second busbar that extends in the arrangement direction of the terminals from anend of the first bus bar and is connected to a terminal of one of thesome condensers.
 6. A power converter as claimed in claim 1, furthercomprising a plurality of straight bus bars that respectively correspondto the phases and are arranged to extend in parallel with one another,wherein the some condensers are arranged to be angled relative to thesebus bars.
 7. A power converter as claimed in claim 6, in which each ofthe straight bus bars connects respective input terminals of the firstand second switching elements that correspond to the same phase.
 8. Apower converter as claimed in claim 1, in which an arrangement directionof the some of the plurality of condensers and a direction of the linesformed by the terminals form an acute non-zero angle.
 9. A powerconverter as claimed in claim 4, in which the wirings for connecting theother condensers to the phases are arranged to be at an acute non-zeroangle relative to the arrangement direction of the terminals.
 10. Apower converter as claimed in claim 6, wherein the some condensers arearranged to be at an acute non-zero angle relative to the bus bars.